In a nuclear power station, it is necessary to be able to purge the circuits which are not used in a continuous manner, such as the shut-down cooling circuit and, more generally, all the parts of the circuits which can be isolated.
It is also necessary to be able to purge those enclosures which are likely to hold liquids or gases which are contaminated by radioactive substances coming from the reactor core.
This purging operation can be carried out during cold close-down periods, and requires certain precautions to be taken, as the liquids or gases remaining in the circuits being purged are generally contaminated by radioactive substances coming from the reactor core.
At present, collecting networks are used which are connected directly to the various components of the piping system and to the pieces of equipment which are being purged. These networks are provided with inspection windows which permit visual inspection of the flow during purging and are connected in a permanent manner to the circuits from which they are intended to collect the purged liquids and gases.
As the points in the piping system where purging or drainage has to be carried out are many in number and are distributed throughout the circuit to be purged, the circuit for collecting the removed liquids and gases is generally complicated and of appreciable length.
The length of piping constituting this network for collecting such liquids and gases rapidly becomes contaminated since it is only rarely that fluids pass through them, and thus conditions are created under which it is fairly easy for radioactive deposits to be formed there. Some of these pipes become contaminated to such a degree that they have to be replaced during the life of the power station.
When the drainage of the liquids contained in the piping or the equipment to be purged has been completed, the section of piping which has been purged is filled with air, which, when the piping system is being filled, escapes through vents, carrying with it a small amount of liquid which contains radioactive products.
It is consequently necessary to send this air through a phase separator before releasing the gaseous phase into the atmosphere of the building.
The collected contaminated liquids are sent to an installation for treating the contaminated effluent in which the radioactive products are eliminated.
Installations for collecting the drained liquids and gases in the circuits constituting the equipment of nuclear power stations are consequently very complex and involved and increase the constructional costs of the latter.
The object of the invention is consequently to provide a device for collecting the purged liquid and gases in an installation containing substances which may possess a certain degree of radioactivity, and including closable purging means distributed at different locations in the installation, such device making it possible to avoid the use of complex piping networks connected in a permanent manner to the installation.
In order to achieve this object, the self-contained and movable collecting device comprises:
(a) a removable and transportable enclosure of small dimensions which can be connected to the purging means of the installation, in such a way that the internal volume of the enclosure is isolated from the external medium;
(b) a means for opening or closing the purging means which can be operated from outside the enclosure for isolating the inside of the enclosure from the installation to be purged or putting these two in communication;
(c) a movable unit for drawing off and collecting the purged liquids and gases, including at least one collecting reservoir, a suction means arranged inside this reservoir, a means for evacuating gases into the atmosphere and a connecting component for evacuation of the purged liquids into a treatment installation;
(d) a flexible connecting pipe between the enclosure and the drawing-off and collecting unit.
A description will now be given, with reference to the attached drawings, of one embodiment of a device for collecting purge liquid and gases which can for example, be used in a pressurized water nuclear power station, for purging the cooling circuit of the shut-down reactor.